Hi Markeo,
Those two letters are, a single letter for “bold” (not supported by the dictionaries but it is used in html) followed by another single letter which is indicated by “bit of..” the word that follows.
Me too. I can't access the interactive version. It is blocked by a message asking for subscription. I found I could access it on a different device with a different email address. So it looks like one can get a limited number of puzzles without subscribing.
Happy New Year,
Sorry, Barry C, I can’t parse 23d either, but I have completed this satisfying and challenging crossword.
Can’t parse last word in 25a.
COD:22a.